Building Containerized Microservices in Golang

With the constant updates in web apps and development architecture, microservices have emerged as the latest trend in the architecture for developing applications. The advancements in application design, coupled with protocols for container transport, have opened new doors toward speed and efficiency in development.

Containerizing all microservices applications can help open doors toward better agile development and increased delivery rate. In this article, we take a look at just how easy it can be to create containerized services within the microservice environment. Stay with us as we run you through the process, and also look at the code required for the same.

Steps for Containerized Microservice Development in Golang

We now look at the steps required for creating containerized services in Golang.

Watermark  

The first step is to create a Watermark service within the pkg folder. Developers can create a new file by the name of service.go in the package folder.

import (
	"context"


	"github.com/velotiotech/watermark-service/internal"
)


type Service interface {
	// Get the list of all documents
	Get(ctx context.Context, filters ...internal.Filter) ([]internal.Document, error)
	Status(ctx context.Context, ticketID string) (internal.Status, error)
	Watermark(ctx context.Context, ticketID, mark string) (int, error)
	AddDocument(ctx context.Context, doc *internal.Document) (string, error)
	ServiceStatus(ctx context.Context) (int, error)
}

Implementing the Service

The next step is to implement the service. The code below will instantaneously update and implement the service:

import (
	"context"
	"net/http"
	"os"


	"github.com/velotiotech/watermark-service/internal"


	"github.com/go-kit/kit/log"
	"github.com/lithammer/shortuuid/v3"
)


type watermarkService struct{}


func NewService() Service { return &watermarkService{} }


func (w *watermarkService) Get(_ context.Context, filters ...internal.Filter) ([]internal.Document, error) {
	// query the database using the filters and return the list of documents
	// return error if the filter (key) is invalid and also return error if no item found
	doc := internal.Document{
		Content: "book",
		Title:   "Harry Potter and Half Blood Prince",
		Author:  "J.K. Rowling",
		Topic:   "Fiction and Magic",
	}
	return []internal.Document{doc}, nil
}


func (w *watermarkService) Status(_ context.Context, ticketID string) (internal.Status, error) {
	// query database using the ticketID and return the document info
	// return err if the ticketID is invalid or no Document exists for that ticketID
	return internal.InProgress, nil
,,,,}


func (w *watermarkService) Watermark(_ context.Context, ticketID, mark string) (int, error) {
	// update the database entry with watermark field as non empty
	// first check if the watermark status is not already in InProgress, Started or Finished state
	// If yes, then return invalid request
	// return error if no item found using the ticketID
	return http.StatusOK, nil
}


func (w *watermarkService) AddDocument(_ context.Context, doc *internal.Document) (string, error) {
	// add the document entry in the database by calling the database service
	// return error if the doc is invalid and/or the database invalid entry error
	newTicketID := shortuuid.New()
	return newTicketID, nil
}


func (w *watermarkService) ServiceStatus(_ context.Context) (int, error) {
	logger.Log("Checking the Service health...")
	return http.StatusOK, nil
}


var logger log.Logger


func init() {
	logger = log.NewLogfmtLogger(log.NewSyncWriter(os.Stderr))
	logger = log.With(logger, "ts", log.DefaultTimestampUTC)
}

Create Endpoints Package

The next step is to create and establish an endpoint service. The endpoint service will contain two files. The first file will be for recognizing endpoint requests. While the second file will be for storing all responses.

import "github.com/velotiotech/watermark-service/internal"


type GetRequest struct {
	Filters []internal.Filter `json:"filters,omitempty"`
}


type GetResponse struct {
	Documents []internal.Document `json:"documents"`
	Err       string              `json:"err,omitempty"`
}


type StatusRequest struct {
	TicketID string `json:"ticketID"`
}


type StatusResponse struct {
	Status internal.Status `json:"status"`
	Err    string          `json:"err,omitempty"`
}


type WatermarkRequest struct {
	TicketID string `json:"ticketID"`
	Mark     string `json:"mark"`
}


type WatermarkResponse struct {
	Code int    `json:"code"`
	Err  string `json:"err"`
}


type AddDocumentRequest struct {
	Document *internal.Document `json:"document"`
}


type AddDocumentResponse struct {
	TicketID string `json:"ticketID"`
	Err      string `json:"err,omitempty"`
}


type ServiceStatusRequest struct{}


type ServiceStatusResponse struct {
	Code int    `json:"status"`
	Err  string `json:"err,omitempty"`
}

Additionally, we will also create a file by the name of endpoints.go. This file will ensure smooth operations of the code:

import (
	"context"
	"errors"
	"os"


	"github.com/aayushrangwala/watermark-service/internal"
	"github.com/aayushrangwala/watermark-service/pkg/watermark"


	"github.com/go-kit/kit/endpoint"
	"github.com/go-kit/kit/log"
)


type Set struct {
	GetEndpoint           endpoint.Endpoint
	AddDocumentEndpoint   endpoint.Endpoint
	StatusEndpoint        endpoint.Endpoint
	ServiceStatusEndpoint endpoint.Endpoint
	WatermarkEndpoint     endpoint.Endpoint
}


func NewEndpointSet(svc watermark.Service) Set {
	return Set{
		GetEndpoint:           MakeGetEndpoint(svc),
		AddDocumentEndpoint:   MakeAddDocumentEndpoint(svc),
		StatusEndpoint:        MakeStatusEndpoint(svc),
		ServiceStatusEndpoint: MakeServiceStatusEndpoint(svc),
		WatermarkEndpoint:     MakeWatermarkEndpoint(svc),
	}
}


func MakeGetEndpoint(svc watermark.Service) endpoint.Endpoint {
	return func(ctx context.Context, request interface{}) (interface{}, error) {
		req := request.(GetRequest)
		docs, err := svc.Get(ctx, req.Filters...)
		if err != nil {
			return GetResponse{docs, err.Error()}, nil
		}
		return GetResponse{docs, ""}, nil
	}
}


func MakeStatusEndpoint(svc watermark.Service) endpoint.Endpoint {
	return func(ctx context.Context, request interface{}) (interface{}, error) {
		req := request.(StatusRequest)
		status, err := svc.Status(ctx, req.TicketID)
		if err != nil {
			return StatusResponse{Status: status, Err: err.Error()}, nil
		}
		return StatusResponse{Status: status, Err: ""}, nil
	}
}


func MakeAddDocumentEndpoint(svc watermark.Service) endpoint.Endpoint {
	return func(ctx context.Context, request interface{}) (interface{}, error) {
		req := request.(AddDocumentRequest)
		ticketID, err := svc.AddDocument(ctx, req.Document)
		if err != nil {
			return AddDocumentResponse{TicketID: ticketID, Err: err.Error()}, nil
		}
		return AddDocumentResponse{TicketID: ticketID, Err: ""}, nil
	}
}


func MakeWatermarkEndpoint(svc watermark.Service) endpoint.Endpoint {
	return func(ctx context.Context, request interface{}) (interface{}, error) {
		req := request.(WatermarkRequest)
		code, err := svc.Watermark(ctx, req.TicketID, req.Mark)
		if err != nil {
			return WatermarkResponse{Code: code, Err: err.Error()}, nil
		}
		return WatermarkResponse{Code: code, Err: ""}, nil
	}
}


func MakeServiceStatusEndpoint(svc watermark.Service) endpoint.Endpoint {
	return func(ctx context.Context, request interface{}) (interface{}, error) {
		_ = request.(ServiceStatusRequest)
		code, err := svc.ServiceStatus(ctx)
		if err != nil {
			return ServiceStatusResponse{Code: code, Err: err.Error()}, nil
		}
		return ServiceStatusResponse{Code: code, Err: ""}, nil
	}
}


func (s *Set) Get(ctx context.Context, filters ...internal.Filter) ([]internal.Document, error) {
	resp, err := s.GetEndpoint(ctx, GetRequest{Filters: filters})
	if err != nil {
		return []internal.Document{}, err
	}
	getResp := resp.(GetResponse)
	if getResp.Err != "" {
		return []internal.Document{}, errors.New(getResp.Err)
	}
	return getResp.Documents, nil
}


func (s *Set) ServiceStatus(ctx context.Context) (int, error) {
	resp, err := s.ServiceStatusEndpoint(ctx, ServiceStatusRequest{})
	svcStatusResp := resp.(ServiceStatusResponse)
	if err != nil {
		return svcStatusResp.Code, err
	}
	if svcStatusResp.Err != "" {
		return svcStatusResp.Code, errors.New(svcStatusResp.Err)
	}
	return svcStatusResp.Code, nil
}


func (s *Set) AddDocument(ctx context.Context, doc *internal.Document) (string, error) {
	resp, err := s.AddDocumentEndpoint(ctx, AddDocumentRequest{Document: doc})
	if err != nil {
		return "", err
	}
	adResp := resp.(AddDocumentResponse)
	if adResp.Err != "" {
		return "", errors.New(adResp.Err)
	}
	return adResp.TicketID, nil
}


func (s *Set) Status(ctx context.Context, ticketID string) (internal.Status, error) {
	resp, err := s.StatusEndpoint(ctx, StatusRequest{TicketID: ticketID})
	if err != nil {
		return internal.Failed, err
	}
	stsResp := resp.(StatusResponse)
	if stsResp.Err != "" {
		return internal.Failed, errors.New(stsResp.Err)
	}
	return stsResp.Status, nil
}


func (s *Set) Watermark(ctx context.Context, ticketID, mark string) (int, error) {
	resp, err := s.WatermarkEndpoint(ctx, WatermarkRequest{TicketID: ticketID, Mark: mark})
	wmResp := resp.(WatermarkResponse)
	if err != nil {
		return wmResp.Code, err
	}
	if wmResp.Err != "" {
		return wmResp.Code, errors.New(wmResp.Err)
	}
	return wmResp.Code, nil
}


var logger log.Logger


func init() {
	logger = log.NewLogfmtLogger(log.NewSyncWriter(os.Stderr))
	logger = log.With(logger, "ts", log.DefaultTimestampUTC)
}

Create a http.go File

Next, we will create a http.go file to transport functions through the course of the service:

	import (
		"context"
		"encoding/json"
		"net/http"
		"os"
	

		"github.com/velotiotech/watermark-service/internal/util"
		"github.com/velotiotech/watermark-service/pkg/watermark/endpoints"
	

		"github.com/go-kit/kit/log"
		httptransport "github.com/go-kit/kit/transport/http"
	)
	

	func NewHTTPHandler(ep endpoints.Set) http.Handler {
		m := http.NewServeMux()
	

		m.Handle("/healthz", httptransport.NewServer(
			ep.ServiceStatusEndpoint,
			decodeHTTPServiceStatusRequest,
			encodeResponse,
		))
		m.Handle("/status", httptransport.NewServer(
			ep.StatusEndpoint,
			decodeHTTPStatusRequest,
			encodeResponse,
		))
		m.Handle("/addDocument", httptransport.NewServer(
			ep.AddDocumentEndpoint,
			decodeHTTPAddDocumentRequest,
			encodeResponse,
		))
		m.Handle("/get", httptransport.NewServer(
			ep.GetEndpoint,
			decodeHTTPGetRequest,
			encodeResponse,
		))
		m.Handle("/watermark", httptransport.NewServer(
			ep.WatermarkEndpoint,
			decodeHTTPWatermarkRequest,
			encodeResponse,
		))
	

		return m
	}
	

	func decodeHTTPGetRequest(_ context.Context, r *http.Request) (interface{}, error) {
		var req endpoints.GetRequest
		if r.ContentLength == 0 {
			logger.Log("Get request with no body")
			return req, nil
		}
		err := json.NewDecoder(r.Body).Decode(&req)
		if err != nil {
			return nil, err
		}
		return req, nil
	}
	

	func decodeHTTPStatusRequest(ctx context.Context, r *http.Request) (interface{}, error) {
		var req endpoints.StatusRequest
		err := json.NewDecoder(r.Body).Decode(&req)
		if err != nil {
			return nil, err
		}
		return req, nil
	}
	

	func decodeHTTPWatermarkRequest(_ context.Context, r *http.Request) (interface{}, error) {
		var req endpoints.WatermarkRequest
		err := json.NewDecoder(r.Body).Decode(&req)
		if err != nil {
			return nil, err
		}
		return req, nil
	}
	

	func decodeHTTPAddDocumentRequest(_ context.Context, r *http.Request) (interface{}, error) {
		var req endpoints.AddDocumentRequest
		err := json.NewDecoder(r.Body).Decode(&req)
		if err != nil {
			return nil, err
		}
		return req, nil
	}
	

	func decodeHTTPServiceStatusRequest(_ context.Context, _ *http.Request) (interface{}, error) {
		var req endpoints.ServiceStatusRequest
		return req, nil
	}
	

	func encodeResponse(ctx context.Context, w http.ResponseWriter, response interface{}) error {
		if e, ok := response.(error); ok && e != nil {
			encodeError(ctx, e, w)
			return nil
		}
		return json.NewEncoder(w).Encode(response)
	}
	

	func encodeError(_ context.Context, err error, w http.ResponseWriter) {
		w.Header().Set("Content-Type", "application/json; charset=utf-8")
		switch err {
		case util.ErrUnknown:
			w.WriteHeader(http.StatusNotFound)
		case util.ErrInvalidArgument:
			w.WriteHeader(http.StatusBadRequest)
		default:
			w.WriteHeader(http.StatusInternalServerError)
		}
		json.NewEncoder(w).Encode(map[string]interface{}{
			"error": err.Error(),
		})
	}
	

	var logger log.Logger
	

	func init() {
		logger = log.NewLogfmtLogger(log.NewSyncWriter(os.Stderr))
		logger = log.With(logger, "ts", log.DefaultTimestampUTC)
	}

We will also create a file by the name of grpc.go to define the map of protobuf payload. 

import (
	"context"


	"github.com/velotiotech/watermark-service/api/v1/pb/watermark"


	"github.com/velotiotech/watermark-service/internal"
	"github.com/velotiotech/watermark-service/pkg/watermark/endpoints"


	grpctransport "github.com/go-kit/kit/transport/grpc"
)


type grpcServer struct {
	get           grpctransport.Handler
	status        grpctransport.Handler
	addDocument   grpctransport.Handler
	watermark     grpctransport.Handler
	serviceStatus grpctransport.Handler
}


func NewGRPCServer(ep endpoints.Set) watermark.WatermarkServer {
	return &grpcServer{
		get: grpctransport.NewServer(
			ep.GetEndpoint,
			decodeGRPCGetRequest,
			decodeGRPCGetResponse,
		),
		status: grpctransport.NewServer(
			ep.StatusEndpoint,
			decodeGRPCStatusRequest,
			decodeGRPCStatusResponse,
		),
		addDocument: grpctransport.NewServer(
			ep.AddDocumentEndpoint,
			decodeGRPCAddDocumentRequest,
			decodeGRPCAddDocumentResponse,
		),
		watermark: grpctransport.NewServer(
			ep.WatermarkEndpoint,
			decodeGRPCWatermarkRequest,
			decodeGRPCWatermarkResponse,
		),
		serviceStatus: grpctransport.NewServer(
			ep.ServiceStatusEndpoint,
			decodeGRPCServiceStatusRequest,
			decodeGRPCServiceStatusResponse,
		),
	}
}


func (g *grpcServer) Get(ctx context.Context, r *watermark.GetRequest) (*watermark.GetReply, error) {
	_, rep, err := g.get.ServeGRPC(ctx, r)
	if err != nil {
		return nil, err
	}
	return rep.(*watermark.GetReply), nil
}


func (g *grpcServer) ServiceStatus(ctx context.Context, r *watermark.ServiceStatusRequest) (*watermark.ServiceStatusReply, error) {
	_, rep, err := g.get.ServeGRPC(ctx, r)
	if err != nil {
		return nil, err
	}
	return rep.(*watermark.ServiceStatusReply), nil
}


func (g *grpcServer) AddDocument(ctx context.Context, r *watermark.AddDocumentRequest) (*watermark.AddDocumentReply, error) {
	_, rep, err := g.addDocument.ServeGRPC(ctx, r)
	if err != nil {
		return nil, err
	}
	return rep.(*watermark.AddDocumentReply), nil
}


func (g *grpcServer) Status(ctx context.Context, r *watermark.StatusRequest) (*watermark.StatusReply, error) {
	_, rep, err := g.status.ServeGRPC(ctx, r)
	if err != nil {
		return nil, err
	}
	return rep.(*watermark.StatusReply), nil
}


func (g *grpcServer) Watermark(ctx context.Context, r *watermark.WatermarkRequest) (*watermark.WatermarkReply, error) {
	_, rep, err := g.watermark.ServeGRPC(ctx, r)
	if err != nil {
		return nil, err
	}
	return rep.(*watermark.WatermarkReply), nil
}


func decodeGRPCGetRequest(_ context.Context, grpcReq interface{}) (interface{}, error) {
	req := grpcReq.(*watermark.GetRequest)
	var filters []internal.Filter
	for _, f := range req.Filters {
		filters = append(filters, internal.Filter{Key: f.Key, Value: f.Value})
	}
	return endpoints.GetRequest{Filters: filters}, nil
}


func decodeGRPCStatusRequest(_ context.Context, grpcReq interface{}) (interface{}, error) {
	req := grpcReq.(*watermark.StatusRequest)
	return endpoints.StatusRequest{TicketID: req.TicketID}, nil
}


func decodeGRPCWatermarkRequest(_ context.Context, grpcReq interface{}) (interface{}, error) {
	req := grpcReq.(*watermark.WatermarkRequest)
	return endpoints.WatermarkRequest{TicketID: req.TicketID, Mark: req.Mark}, nil
}


func decodeGRPCAddDocumentRequest(_ context.Context, grpcReq interface{}) (interface{}, error) {
	req := grpcReq.(*watermark.AddDocumentRequest)
	doc := &internal.Document{
		Content:   req.Document.Content,
		Title:     req.Document.Title,
		Author:    req.Document.Author,
		Topic:     req.Document.Topic,
		Watermark: req.Document.Watermark,
	}
	return endpoints.AddDocumentRequest{Document: doc}, nil
}


func decodeGRPCServiceStatusRequest(_ context.Context, grpcReq interface{}) (interface{}, error) {
	return endpoints.ServiceStatusRequest{}, nil
}


func decodeGRPCGetResponse(_ context.Context, grpcReply interface{}) (interface{}, error) {
	reply := grpcReply.(*watermark.GetReply)
	var docs []internal.Document
	for _, d := range reply.Documents {
		doc := internal.Document{
			Content:   d.Content,
			Title:     d.Title,
			Author:    d.Author,
			Topic:     d.Topic,
			Watermark: d.Watermark,
		}
		docs = append(docs, doc)
	}
	return endpoints.GetResponse{Documents: docs, Err: reply.Err}, nil
}


func decodeGRPCStatusResponse(_ context.Context, grpcReply interface{}) (interface{}, error) {
	reply := grpcReply.(*watermark.StatusReply)
	return endpoints.StatusResponse{Status: internal.Status(reply.Status), Err: reply.Err}, nil
}


func decodeGRPCWatermarkResponse(ctx context.Context, grpcReply interface{}) (interface{}, error) {
	reply := grpcReply.(*watermark.WatermarkReply)
	return endpoints.WatermarkResponse{Code: int(reply.Code), Err: reply.Err}, nil
}


func decodeGRPCAddDocumentResponse(ctx context.Context, grpcReply interface{}) (interface{}, error) {
	reply := grpcReply.(*watermark.AddDocumentReply)
	return endpoints.AddDocumentResponse{TicketID: reply.TicketID, Err: reply.Err}, nil
}


func decodeGRPCServiceStatusResponse(ctx context.Context, grpcReply interface{}) (interface{}, error) {
	reply := grpcReply.(*watermark.ServiceStatusReply)
	return endpoints.ServiceStatusResponse{Code: int(reply.Code), Err: reply.Err}, nil
}

The service will now be ready for implementation, and your containerized microservices in Golang can be shared with the client. You can also convert the entire interface to a service file. This blog already assumes that you know how to create a pb file. You can generate a pb file by following one of the paths above and using the proto file.